In aboveground storage tanks, corrosion of soil side bottoms and double bottoms is unpredictable and can reduce the thickness of the tank bottom up to about 5 mm/year. A typical corrosion protection method, i.e., cathodic protection system (CPS), in most cases is not effective by itself due to inherent dry soil conditions at least during some part of a year as well as issues with tank design and geometry that creates holidays in the cathodic protection. The use of SCI, as with CPS, is only viable in fully saturated sand or soil and it is generally difficult to obtain such saturated conditions. Protective coatings cannot be applied to existing soil side tank bottoms. Any protective coatings applied to the soil side tank bottoms will be destroyed in the weld zones and may actually accelerate corrosion in those areas.
In summary, soil side corrosion of aboveground storage tanks either with a single bottom or a double bottom is a major worldwide problem. Such tanks face unpredictable application and environmental conditions that often cause the bottoms to leak. Moreover, dangerous operating conditions occur when the leaking product is volatile or flammable. Another disadvantage is that repair of tank bottoms generally requires down time.